The rendering of three-dimensional (3D) graphical images is of interest in a variety of electronic games and other applications. Rendering is the general term that describes the overall multi-step process of transitioning from a database representation of a 3D object to a pseudo realistic two-dimensional projection of the object onto a viewing surface.
The rendering process involves a number of steps, such as, for example, setting up a polygon model that contains the information which is subsequently required by shading/texturing processes, applying linear transformations to the polygon mesh model, culling back facing polygons, clipping the polygons against a view volume, scan converting/rasterizing the polygons to a pixel coordinate set, and shading/lighting the individual pixels using interpolated or incremental shading techniques.
Graphics Processing Units (GPUs) are specialized integrated circuit devices that are commonly used in graphics systems to accelerate the performance of a 3D rendering application. GPUs are commonly used in conjunction with a central processing unit (CPU) to generate 3D images for one or more applications executing on a computer system. Modern GPUs typically utilize a graphics pipeline for processing data.
The power of modern GPU sub-systems (e.g., add-in graphics cards, etc.) is increasingly comprising a larger share of the overall value of a desktop computer system and can rival the complexity and sophistication of a computer system's CPU. A modern GPU can comprise an integrated circuit device having over 200 million transistors and running at several hundred megahertz. Such a modern GPU can consume hundreds of watts of power and require carefully designed thermal protection components (e.g., heat sink fans, access to adequate airflow, etc.).
Generally, the layout and performance of GPU subsystems (e.g., GPU graphics cards) are constrained by a number of overall system design factors. GPU subsystems are generally designed to interface with an ATX compliant computer system motherboard. The ATX form factor refers to the widely used industry standard motherboard form factor supported by the leading industry manufacturers. Such manufactures include, for example, CPU manufacturers, chipset manufacturers, motherboard manufacturers, and the like.
For example, the ATX form factor allows a limited amount of space for a card-based GPU. A typical card-based GPU connects to the motherboard via an AGP slot. The AGP slot has a limited amount of space for the components of the card-based GPU. The limited amount of space directly impacts the efficiency of the thermal protection components of the card-based GPU. Additionally, as card-based GPUs have increased in performance, the available power (e.g., the specified voltages and currents) of the AGP connection has become increasingly insufficient.
The BTX form factor refers to a more recent industry standard motherboard form factor. The BTX form factor is generally considered the next generation ATX follow on specification for a “desktop” PC chassis and, as with the earlier ATX form factor, is widely supported by the leading industry manufacturers. Unfortunately, the BTX form factor persons even more problems with respect to high-performance GPU subsystems.
The BTX form factor is problematic in that the BTX design rules place a number of constraints on the form and performance of the GPU subsystem. For example, BTX design rules locate the desktop computer system's CPU at the front entry point for cooling airflow, while positioning the GPU subsystem (e.g., graphics card) in its downstream airflow and adding restrictions on the GPU subsystem's physical dimensions (e.g., x-y-z size), available air flow, available thermal dissipation, and power delivery.
Similar constraints are in place for laptop computer system form factors. For example, the future evolution of GPU subsystems for laptop computers is constrained by the fact that the laptop chassis (e.g., motherboard platform, case, airflow, etc.) is optimized for the requirements of CPUs and their associated chipsets. This optimization limits the available thermal dissipation budget, power delivery, and physical dimensions (e.g., x-y-z size) for any graphics subsystem implementation.
Constraints are also placed on the future performance evolution of GPU subsystems by some newly emerging industry standards. PCI express is one such standard. Some versions of the PCI express standard specify a maximum power available for a coupled device (e.g., 150 W prescribed by the PCI SIG specification for PCI Express Graphics). As GPU subsystem performance continues to evolve, the requirements of high-end GPU implementations may greatly exceed the specified maximum power available. In addition to inadequate power, some versions of the PCI express standard specify an insufficient amount of bandwidth between the GPU subsystem and the rest of the computer system platform (e.g., system memory, CPU, etc.). The insufficient bandwidth limits the upward scalability of the GPU subsystem performance by bottlenecking data pathways between the GPU subsystem and the computer system platform resources.